U.S. patent application number 10/701440 was filed with the patent office on 2005-06-02 for production method of polyamide.
Invention is credited to Kikuchi, Minoru, Kurose, Hideyuki, Shida, Takatoshi, Tanaka, Kazumi.
Application Number | 20050119446 10/701440 |
Document ID | / |
Family ID | 32110665 |
Filed Date | 2005-06-02 |
United States Patent
Application |
20050119446 |
Kind Code |
A1 |
Tanaka, Kazumi ; et
al. |
June 2, 2005 |
Production method of polyamide
Abstract
In the production method of polyamide of the present invention,
the mole balance at a set point during melt polymerization is
estimated from a pre-established equation for calculating the mole
balance during melt polymerization from a melt viscosity. On the
basis of the estimated mole balance, the subsequent conditions of
melt polymerization of a batch and the polymerization conditions of
the next and subsequent batches are determined. In addition, the
mole balance, molecular weight and relative viscosity of
melt-polymerized polyamide are estimated from pre-established
equations each for respectively calculating the mole balance,
molecular weight and relative viscosity at the end point of melt
polymerization from the melt viscosity. The conditions for solid
phase-polymerizing the melt-polymerized polyamide are determined on
the basis of estimated values.
Inventors: |
Tanaka, Kazumi; (Niigata,
JP) ; Kurose, Hideyuki; (Niigata, JP) ; Shida,
Takatoshi; (Niigata, JP) ; Kikuchi, Minoru;
(Niigata, JP) |
Correspondence
Address: |
ANTONELLI, TERRY, STOUT & KRAUS, LLP
1300 NORTH SEVENTEENTH STREET
SUITE 1800
ARLINGTON
VA
22209-3873
US
|
Family ID: |
32110665 |
Appl. No.: |
10/701440 |
Filed: |
November 6, 2003 |
Current U.S.
Class: |
528/310 |
Current CPC
Class: |
C08G 69/28 20130101;
C08G 69/04 20130101 |
Class at
Publication: |
528/310 |
International
Class: |
C08G 069/08 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 7, 2002 |
JP |
324089/2002 |
Nov 7, 2002 |
JP |
324090/2002 |
Nov 7, 2002 |
JP |
324091/2002 |
Claims
What is claimed is:
1. A production method of polyamide by batch melt polymerization,
which comprises a step of developing at least one estimating
equation selected from the group consisting of an estimating
equation for calculating a mole balance (diamine unit/carboxylic
acid unit) of polyamide under melt polymerization from a melt
viscosity of polyamide measured at a set point during the melt
polymerization, an estimating equation for calculating a molecular
weight of polyamide under melt polymerization from the melt
viscosity, and an estimating equation for calculating a relative
viscosity of polyamide under melt polymerization from the melt
viscosity; and a step of estimating using said at least one
estimating equation at least one property selected from the group
consisting of a mole balance, a molecular weight and a relative
viscosity of polyamide under melt polymerization from a melt
viscosity of polyamide measured at a set point during melt
polymerization in next and subsequent batches.
2. The production method according to claim 1, wherein
polymerization conditions (time, pressure, temperature) until the
polyamide is discharged from a polymerization vessel are determined
on the basis of the estimated mole balance.
3. The production method according to claim 1, wherein the
estimating equation for calculating the mole balance is a linear
equation represented by the following Equation A: Mole
balance=a.times.MV+b (A) wherein MV is melt viscosity (Pa.s), and a
and b are empirical constants.
4. The production method according to claim 1, wherein
polymerization conditions (time, pressure, temperature) until the
polyamide is discharged from a polymerization vessel are determined
on the basis of the estimated molecular weight.
5. The production method according to claim 1, wherein
polymerization conditions (time, pressure, temperature) until the
polyamide is discharged from a polymerization vessel are determined
on the basis of the estimated relative viscosity.
6. The production method according to claim 1, wherein the melt
viscosity of polyamide is calculated from a measured stirring
torque using an estimating equation which is developed from a
relationship between the melt viscosity and the stirring torque
generated by a rotation of stirring blade for stirring and mixing
the polyamide.
7. The production method according to claim 6, wherein a pressure
of a batch polymerization vessel at the measurement of the stirring
torque is in a variation range within .+-.10 kPa of an average
pressure between batches conducted for developing the estimating
equation.
8. The production method according to claim 1, wherein the set
point during melt polymerization is determined by a temperature of
polyamide in a batch polymerization vessel.
9. The production method according to claim 1, wherein the set
point during melt polymerization is determined by a time taken from
initiation of amidation reaction.
10. The production method according to claim 1, wherein a total
amount of a polyamide of a previous batch remaining in a batch
polymerization vessel and starting materials for polyamide charged
at the beginning of melt polymerization is in a variation range
within .+-.{fraction (1/50)} of an average total amount between
batches conducted for developing the estimating equation.
11. The production method according to claim 1, wherein the melt
polymerization for producing polyamide in a batch polymerization
vessel is conducted by directly adding a diamine component to a
molten dicarboxylic acid component in the absence of solvent.
12. The production method according to claim 11, wherein the mole
balance of polyamide under melt polymerization is estimated from
the melt viscosity at the set point during melt polymerization, and
an addition amount of the diamine component is controlled on the
basis of the estimated mole balance.
13. The production method according to claim 11, wherein the
diamine component comprises 70 mol % or more of xylylene
diamine.
14. The production method according to claim 11, wherein the
diamine component comprises 70 mol % or more of
bis(aminomethyl)cyclohexane.
15. The production method according to claim 11, wherein the
dicarboxylic acid component comprises 50 mol % or more of adipic
acid.
16. A production method of polyamide by solid phase polymerization
of batch melt-polymerized polyamide, which comprises: (1)
developing an estimating equation for calculating a mole balance
(diamine unit/carboxylic acid unit) of polyamide under melt
polymerization from a melt viscosity of polyamide measured at a set
point during the melt polymerization, and calculating a mole
balance of polyamide at the set point during the melt
polymerization of next and subsequent batches from the estimating
equation; (2) developing an estimating equation for calculating a
molecular weight or relative viscosity of polyamide from the melt
viscosity, and calculating a molecular weight or relative viscosity
at an end point of the melt polymerization of next and subsequent
batches from the estimating equation; and (3) determining
conditions (temperature, time and pressure) of the solid phase
polymerization of the melt-polymerized polyamide on the basis of
the calculated values in the steps (1) and (2).
17. The production method according to claim 16, wherein the
estimating equation for calculating the mole balance is represented
by the following Equation A for a mole balance range of 0.997 or
less, and 1.003 or more: Mole balance=a.times.MV+b (A) wherein MV
is melt viscosity (Pa.s), and a and b are empirical constants.
18. The production method according to claim 16, wherein the set
point during melt polymerization is determined by a temperature of
polyamide in a batch polymerization vessel.
19. The production method according to claim 16, wherein the set
point during melt polymerization is determined by a time taken from
initiation of amidation reaction.
20. The production method according to claim 16, wherein the
estimating equation for calculating the molecular weight of
polyamide from the melt viscosity at the end point of melt
polymerization is represented by the following Equation B:
c.times.log(MW)=log(MV)+d/T+e (B) wherein MW is molecular weight,
MV is melt viscosity (Pa.s), T is temperature (.degree. C.), and c,
d and e are empirical constants.
21. The production method according to claim 16, wherein the
estimating equation for calculating the relative viscosity of
polyamide from the melt viscosity at the end point of melt
polymerization is represented by the following Equation C:
f.times.log(RV)=log(MV)+g/T+h (C) wherein RV is relative viscosity,
MV is melt viscosity (Pa.s), T is temperature (.degree. C.), and f,
g and h are empirical constants.
22. The production method according to claim 16, wherein the melt
viscosity at the set point during melt polymerization and the melt
viscosity at the end point of melt polymerization are calculated
from a relationship between the melt viscosity and a stirring
torque generated by a rotation of stirring blade for stirring and
mixing polyamide.
23. The production method according to claim 22, wherein a total
amount of a polyamide of a previous batch remaining in a batch
polymerization vessel and starting materials for polyamide charged
at the beginning of melt polymerization is in a variation range
within .+-.{fraction (1/50)} of an average total amount between
batches conducted for establishing the relationship.
24. The production method according to claim 22, wherein a pressure
of a batch polymerization vessel at the measurement of the stirring
torque is in a variation range within .+-.10 kPa of an average
pressure between batches conducted for establishing the
relationship.
25. The production method according to claim 16, wherein the melt
polymerization for producing polyamide in a batch polymerization
vessel is conducted by directly adding a diamine component to a
molten dicarboxylic acid component in the absence of solvent.
26. The production method according to claim 25, wherein the
diamine component comprises 70 mol % or more of xylylene
diamine.
27. The production method according to claim 25, wherein the
diamine component comprises 70 mol % or more of
bis(aminomethyl)cyclohexane.
28. The production method according to claim 25, wherein the
dicarboxylic acid component comprises 50 mol % or more of adipic
acid.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a production method of
polyamides employing a rapid estimation of the mole balance of
polyamides during a melt polymerization process, and more
specifically, relates to a production method of polyamides by melt
polymerization in a batch polymerization vessel employing a rapid
estimation of the mole balance of polyamides under melt
polymerization from a melt viscosity during melt polymerization
process. The present invention further relates to a production
method of polyamides by further solid phase-polymerizing a
melt-polymerized polyamide, more specifically, relates to a
production method of solid phase-polymerized polyamides by the
solid phase polymerization of melt-polymerized polyamides in which
properties of the starting melt-polymerized polyamides are rapidly
and easily estimated to determine solid phase polymerization
conditions (time, temperature, pressure) from the estimated
results. The present invention still further relates to a method of
easily estimating the melt viscosity, more specifically, relates to
a method of calculating the melt viscosity of polyamides from a
stirring torque of a melt polymerization system for producing
polyamides in a batch polymerization vessel.
[0003] 2. Description of the Prior Art
[0004] Generally, a melt-polymerized polyamide is produced by the
dehydrating polycondensation of a diamine monomer and a
dicarboxylic acid monomer, in which the monomers are
melt-polymerized at reaction temperatures higher than the melting
point of polyamide being produced. In the production of polyamide,
it is important to maintain the preset mole balance and the preset
polymerization conditions to ensure the production of polyamide
with uniform and stable quality. Therefore, various methods have
been employed to maintain the preset values of mole balance,
polymerization time, polymerization temperature, polymerization
pressure, etc.
[0005] The mole balance is a particularly important process factor
to be precisely controlled, because it has a significant influence
on the polymerization degree of melt-polymerized polyamide. In
batch polymerization method, however, the escape of diamine out of
the reaction system during polymerization is difficult to avoid and
it is quite difficult to make the escaped amount always uniform
from batch to batch, even if the preset mole balance at the initial
charge of monomers is the same in every batch and the
polymerization conditions are made uniform from batch to batch.
Therefore, the mole balance of polyamide to be produced is out of
control and actually depends how the polymerization proceeds.
[0006] If the mole balance is not uniform from batch to batch, the
polymerization time should be adjusted depending on the
batch-to-batch variation of mole balance to make the polymerization
degree of resultant polyamide uniform from batch to batch. In other
words, if the mole balance varies from batch to batch, the real
time observation of polymerization degree, if possible, would
enable the discharge of polyamide at a stage where the aimed
polymerization degree is reached, thereby making the polymerization
degree of the resultant polyamide stable from batch to batch. The
batch-to-batch stability of polymerization degree of polyamide
would result in the batch-to-batch stability of flow
characteristics, such as melt viscosity, molecular weight and
relative viscosity of molten polyamide, which affect the
moldability and processability.
[0007] The mole balance is generally determined by titration
analysis which takes several hours because a polyamide which is
taken out of a melt polymerization vessel and then solidified is
used as the analyzing sample. The sample is dissolved into a
specific solvent and subjected to neutralization titration to
determine the concentration of terminal carboxyl and the
concentration of terminal amino. From the titration results, the
mole balance is calculated. Therefore, it is difficult to feed back
the measured results of the mole balance in a preceding batch to
the next batch before determining the production conditions. If the
mole balance can be quickly determined during melt polymerization,
a measure quite effective for determining the subsequent melt
polymerization conditions of the same batch or the next batch is
obtained, thereby providing an industrially significant method.
[0008] Japanese Patent Publication No. 48-36957 proposes a
real-time measurement of properties by a viscometer in the
continuous production of polyamide. In the proposed method, the
melt viscosity which is related to the polymerization degree can be
quickly determined during melt polymerization without using
chemical analysis. However, the document is quite silent as to the
measurement of the mole balance. A capillary viscometer is taught
to be generally used. In a batch polymerization, however, the use
of such a viscometer is expected to cause severe difficulty which
is not encountered by a continuous polymerization. The content of
reaction liquid changes from the starting monomers to polyamide
just before discharge, and its viscosity may change from 0.01 to
about 500 Pa.s. If the solubility of the starting material to
polyamide is not sufficient, the capillary is clogged to make a
stable use of viscometer difficult. In addition, the viscometer is
generally an expensive measuring device to increase equipment
cost.
[0009] Recently, an on-line measurement of polymer properties using
a near infrared spectrometer has been proposed. Near infrared ray
is quite suitable for non-destructive analysis and real time
analysis because of its transmitting properties superior to
ultraviolet ray and infrared ray. Problems in stability of light
source, spectrometry system, detector, and hard ware and soft ware
for computing spectra has prevented it from being put into
practical use. Recent development in the technique has solved many
of the problems and the near infrared spectrometer has come into
the market.
[0010] Production methods of polyester in which properties of
polyester are measured using a near infrared spectrometer and the
reaction conditions are controlled by the measured values are
disclosed, for example, in Japanese Patent Application Laid-Open
Nos. 2-306937, 10-182802, 11-60711 and 11-315137. Japanese Patent
Application Laid-Open No. 6-322054 proposes a production method of
phenol resin in which the chemical composition of the system is
measured by a near infrared spectrometer and the reaction is
continued by estimating the progress of reaction on the basis of
measured values. WO 96/05498 discloses a method of controlling the
amount of solvent in a reaction solution by measuring the
concentration of a solution comprising an amide solvent and an
aromatic polyamide using a near infrared spectrometer. WO 96/16107
discloses a production method of polyamide by a continuous melt
polymerization employing a near infrared spectrometer. In the
proposed method, the concentrations of carboxyl end group (terminal
carboxyl) and amino end group (terminal amino) are measured. The
feeding amount of diamine is controlled on the basis of the
measured results to control the ratio between the concentrations of
carboxyl end group and amino end group, thereby attaining the aimed
mole balance and preventing the formation of solid matters in the
reaction apparatus.
[0011] To obtain precise measured results by a near infrared
spectrometer, the solution under measurement should be homogeneous,
requiring the removal of bubbles in the solution. However, the
removal of bubbles are accompanied by a considerable difficulty in
the production of polyamide, because it involves the elimination of
water. In addition, since the lower limit for the measurement by a
near infrared spectrometer is close to the controlling range of
mole balance to be required for polyamide, it is questionable
whether the measured results are effective information. Further, a
near infrared spectrometer is expensive and the installation
thereof into a polymerization vessel requires a considerable cost
in the conversion of polymerization vessel, etc.
[0012] Generally, as a molding polyamide, a polyamide with low
viscosity is used because it is molded by injection molding and so
required to be highly flowable in molten state. In the applications
to bottle, sheet, film and fiber, polyamide is molded also by
extrusion in addition to injection molding. Therefore, polyamide
with moderate to high viscosity is used in the applications to
bottle, sheet, film and fiber because a flowability in molten state
lower than that of the molding polyamide is required.
[0013] As the low viscosity polyamide for use mainly as molding
material, a melt-polymerized polyamide is used as it is or after
drying. If the moderate to high viscosity polyamide for use mainly
as bottle, sheet, film or fiber is intended to produce by melt
polycondensation, a specific polymerization apparatus is required
because a stirring device commonly used cannot generate a stirring
force enough to maintain the uniform molten state in the
polymerization vessel. If the polycondensation is continued from a
low viscosity until a moderate to high viscosity is reached, the
time for maintaining the molten state (reaction time) is prolonged
to cause damage of polyamide molecule (degradation of polymer
molecule due to radical generation) and abnormal reaction such as
non-linear molecule propagation (formation of three-dimensional
polymer), this in turn increasing the formation of gel and fish eye
to invite practical disadvantage. Therefore, the moderate to high
viscosity polyamide has been produced by a solid phase
polymerization in which a low viscosity polyamide is first produced
by a melt polycondensation and then heat-treated in solid
phase.
[0014] The solid phase polymerization of polyamide is generally
conducted by calculating the increase of polymerization degree
during the solid phase polymerization from solid phase
polymerization temperature, time and pressure using a rate equation
of amidation reaction while taking the mole balance and properties
relating to the polymerization degree such as molecular weight and
relative viscosity of the starting polyamide into consideration, by
determining the conditions of solid phase polymerization on the
basis of the calculated results, and by terminating the solid phase
polymerization when the aimed polymerization degree is reached. The
mole balance of the starting polyamide is an important property to
be surely taken into account because it significantly affects the
increasing speed of the polymerization degree. To evaluate the
increasing polymerization degree during the solid phase
polymerization, the polymerization degree of the starting polyamide
is necessary. Thus, the analysis of the properties relating to the
polymerization degree such as molecular weight and relative
viscosity is required before solid phase polymerization.
[0015] A solid phase polymerization without analyzing the starting
polyamide is known, in which polyamide under solid phase
polymerization is sampled and rapidly measured on its melt
viscosity, etc., and the polymerization degree during the solid
phase polymerization is estimated from the measured results thereby
to determine the end point of the solid phase polymerization.
However, since the solid phase polymerization of polyamide is of
high reaction rate as compared with polyester, the solid phase
polymerization of polyamide has limited time for determining its
end point, this making the operation restless.
[0016] If the mole balance and polymerization degree of
melt-polymerized polyamide to be used as the starting material of
the solid phase polymerization are always constant, the analysis is
not required for each time. As mentioned, however, the mole balance
of melt-polymerized polyamide depends on the progress of the
polymerization. The batch-to-batch variation of mole balance
results in the batch-to-batch variation of polymerization degree
(molecular weight, relative viscosity, etc.) which is significantly
affected by the mole balance.
[0017] The mole balance, molecular weight and relative viscosity of
melt-polymerized polyamide are generally chemically analyzed. The
mole balance and number average molecular weight are determined,
for example, from the calculation using the measured values which
are obtained by the measurement of a carboxyl end concentration and
an amino end concentration by neutralization titration of a
solution of polyamide in a specific solvent. The relative viscosity
is determined by dividing a dropping time (second) of a polyamide
solution in concentrated sulfuric acid measured using a viscometer
by a dropping time (second) of sulfuric acid itself. These chemical
analyses usually require 2 to 4 h until the results are obtained.
Therefore, the melt-polymerized polyamide should be stored in a
silo, etc. before solid phase polymerization until the results of
analyses are obtained, thereby preventing the efficient
production.
SUMMARY OF THE INVENTION
[0018] An object of the present invention is to provide a
production method of polyamide by batch melt polymerization
employing a rapid and simple estimation of the mole balance during
the melt polymerization. Another object of the present invention is
to provide a production method of polyamide by solid phase
polymerization of a melt-polymerized polyamide employing a rapid
and simple estimation of the properties of the melt-polymerized
polyamide which are required for determining the conditions of the
solid phase polymerization. Still another object of the present
invention is to provide a production method of polyamide by batch
melt polymerization employing a rapid and simple estimation of the
melt viscosity, molecular weight or relative viscosity of the
polyamide under melt polymerization.
[0019] As a result of extensive study, the inventors have found
that, in the production of polyamide by batch melt polymerization,
the mole balance (diamine unit/dicarboxylic acid unit) of the
polyamide under melt polymerization can be calculated from the melt
viscosity of the polyamide under melt polymerization. The inventors
have further found that the mole balance (diamine unit/dicarboxylic
acid unit), molecular weight and relative viscosity of polyamide
can be calculated from the melt viscosity of polyamide under melt
polymerization, and that the melt-polymerized polyamide is
efficiently solid phase-polymerized by determining the conditions
of the solid phase polymerization from the calculated values. The
inventors still further found that, in the production of polyamide
by batch melt polymerization, the melt viscosity, molecular weight
and relative viscosity of the polyamide under melt polymerization
can be calculated from the stirring torque of polyamide during the
melt polymerization. The present invention has accomplished on the
basis of these findings.
[0020] Thus, the present invention relates to a production method
of polyamide by batch melt polymerization, which comprises a step
of developing at least one estimating equation selected from the
group consisting of an estimating equation for calculating a mole
balance (diamine unit/carboxylic acid unit) of polyamide under melt
polymerization from a melt viscosity of polyamide which is measured
at a set point during the melt polymerization, an estimating
equation for calculating a molecular weight of polyamide under melt
polymerization from the melt viscosity of polyamide, and an
estimating equation for calculating a relative viscosity of
polyamide under melt polymerization from the melt viscosity of
polyamide; and a step of estimating using the estimating equation
at least one property selected from the group consisting of a mole
balance, a molecular weight and a relative viscosity of polyamide
under melt polymerization from a melt viscosity of polyamide which
is measured at a set point during melt polymerization in next and
subsequent batches.
[0021] The present invention further relates to a production method
of polyamide by solid phase polymerization of batch
melt-polymerized polyamide, which comprises (1) developing an
estimating equation for calculating a mole balance (diamine
unit/carboxylic acid unit) of polyamide under melt polymerization
from a melt viscosity of polyamide measured at a set point during
the melt polymerization, and calculating from the estimating
equation the mole balance of polyamide at the set point during the
melt polymerization in next and subsequent batches; (2) developing
an estimating equation for calculating a molecular weight or
relative viscosity of polyamide from the melt viscosity, and
calculating from the estimating equation the molecular weight or
relative viscosity at an end point of the melt polymerization in
next and subsequent batches; and (3) determining conditions
(temperature, time and pressure) of the solid phase polymerization
of the melt-polymerized polyamide from the calculated values in the
steps (1) and (2).
[0022] The present invention still further relates to a production
method of polyamide, in which the melt viscosity for calculating
the mole balance, molecular weight and relative viscosity is
calculated from a stirring torque generated by rotation of stirring
blade for stirring and mixing the polyamide.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is a graph showing one example of the relationship
between the melt viscosity and the mole balance of polyamide under
melt polymerization; and
[0024] FIG. 2 is a graph showing the measured results of relative
viscosity of solid phase-polymerized polyamide.
DETAILED DESCRIPTION OF THE INVENTION
[0025] The set point during the melt polymerization referred to
herein means a measuring point of the melt viscosity in which the
amidation history, which is governed by the rate constant of
amidation, temperature, time, pressure (moisture content), from the
initiation of polymerization to the measurement of melt viscosity
is the same as the history undergone until measuring the melt
viscosity in the process for developing the estimating Equation A
which will be mentioned below. Although not fixed to a particular
stage of the melt polymerization, the set point is preferably at a
middle or later stage of polymerization where the fixation of
monomers is substantially completed, because it is intended to
estimate the mole balance of polyamide under melt polymerization.
To make the history of amidation uniform from batch to batch, it is
operationally easy to use the same additive which affects the rate
constant of amidation reaction and to make the time, temperature
and pressure from the initiation of amidation reaction uniform in
every batch. To determined the set point based on the temperature
of reaction system when the pressure is equal, the polymerization
history until the set point temperature is reached is regulated
constant by controlling the heating conditions by a heating medium,
and the time to be taken from the initiation of amidation reaction
to the set point is regulated preferably within .+-.5 min, more
preferably within .+-.3 min of the average time between batches. To
determined the set point based on the reaction time when the
pressure is equal, the polymerization history until the set point
time is reached is regulated constant by controlling the heating
conditions by a heating medium, and the temperature at the set
point is regulated preferably within .+-.1.degree. C., more
preferably within .+-.0.5.degree. C. of the average temperature
between batches. To regulate the polymerization history uniform by
controlling the heating conditions by a heating medium, total
amount of charged monomers, escaped amount of monomer, and stirring
and mixing efficiency of batch polymerization vessel are required
to be uniform between batches.
[0026] The end point of melt polymerization referred to herein
means a stage just before discharging polyamide from the batch
polymerization vessel, and means that the polyamide solidified by
rapid cooling after discharging and the polyamide present in the
polymerization vessel at the end point of the melt polymerization
have substantially the same properties relating to the
polymerization degree such as molecular weight and relative
viscosity. Unlike the set point during the melt polymerization, the
history of amidation reaction until the end point of the melt
polymerization is not needed to be the same from batch to batch.
However, since the measurement of the melt viscosity is necessary
at the two points (set point and end point), there is no need to
change the history of amidation after the set point between
batches. The difference of the temperatures at the end point of
melt polymerization between batches can be corrected in the
estimating equations B and C, and the temperatures are not
necessary to be the same. However, it is preferred to make the
temperatures uniform to improve the accuracy of the estimation with
minimized error. Thus the batch-to-batch variation of temperature
is regulated preferably within .+-.5.degree. C., more preferably
within .+-.3.degree. C.
[0027] To estimate the mole balance of polyamide from the melt
viscosity at the set point during the melt polymerization, it is
preferred to calculate it from the estimating equation developed
from the actually measured mole balance and melt viscosity in
several batches, preferably in five batches or more. Although the
melt viscosity and the mole balance may be apparently not in
phisicochemical correlation with each other, the mole balance can
be estimated from the melt viscosity with a fair accuracy when the
polymerization history such as temperature, time and pressure until
reaching the set point for measuring the melt viscosity is
uniform.
[0028] The results of simulating the direct polymerization by
adding m-xylylenediamine to molten adipic acid under atmospheric
pressure are shown in FIG. 1. First, in a specific mole balance,
the number average molecular weight of the polyamide obtained at
the set point was calculated using a second-order rate equation of
amidation, while fixing all the reaction conditions such as the
total amount of molten adipic acid and m-xylylene diamine, the
temperature of molten adipic acid when starting the dropwise
addition of m-xylylene diamine, the dropwise addition time of
m-xylylene diamine and the temperature rise history during the
dropwise addition, the temperature of the reaction solution when
completing the dropwise addition of m-xylylene diamine, and the
time and temperature history from completing the dropwise addition
of m-xylylene diamine until reaching the set point. Then, using the
number average molecular weight thus obtained, the melt viscosity
of polyamide at a given temperature was calculated from the
preformulated Equation B to be mentioned below. These series of
calculations were repeated while appropriately changing the mole
balance, and the results thereof were plotted on FIG. 1. As seen
from FIG. 1, the melt viscosity and the mole balance have a
definite correlation with each other, showing that an estimating
equation for calculating the mole balance from the melt viscosity
at the set point during the melt polymerization can be
formulated.
[0029] As seen from FIG. 1, the melt viscosity and the mole balance
are in curved relationship in the mole balance range of 0.997 to
1.003. In this range, the difference in the mole balance is hardly
reflected as the difference in the melt viscosity, and it is
difficult to determine which of dicarboxylic acid and diamine is in
excess in the region centering around mole balance=1. Therefore,
the mole balance is preferably estimated in the mole balance ranges
of 0.997 or less, and 1.003 or more, because from the amounts of
monomers actually added it can be easily determined in these ranges
which of dicarboxylic acid and diamine is in excess. The mole
balance can be easily estimated from the following linear
estimating Equation A:
Mole balance=a.times.MV+b (A)
[0030] wherein MV is melt viscosity (Pa.s), and a and b are
empirical constants.
[0031] The actual mole balance is calculated from the carboxyl end
concentration (terminal carboxyl concentration) and the amino end
concentration (terminal amino concentration) which are measured by
known titration analysis on solidified specimen of sampled reaction
solution. The specimen for the analysis may be a solidified
reaction solution which is taken out at the set point during the
melt polymerization or may be a polyamide taken out after
completing the polymerization if the set point during the melt
polymerization is a later stage of the polymerization where the
escape of monomer no longer occurs.
[0032] To estimate the molecular weight of polyamide from the melt
viscosity at the end point of the melt polymerization, it is
preferred to develop the estimating equation from the molecular
weight and melt viscosity actually measured in several batches,
preferably in five batches or more. For example, the sampled
reaction solution is analyzed by a melt viscometer such as a melt
indexer and a flow tester to measure the melt viscosity and analyze
the molecular weight. The following Equation B is formulated from
the results, by which the molecular weight can be calculated from
the melt viscosity:
c.times.log(W)=log(MV)+d/T+e (B)
[0033] wherein MW is molecular weight, MV is melt viscosity (Pa.s),
T is temperature (.degree. C.), and c, d and e are empirical
constants.
[0034] The molecular weight used herein may be any molecular weight
such as number average molecular weight, weight average molecular
weight and viscosity average molecular weight, and Equation B can
be empirically determined.
[0035] To estimate the relative viscosity of polyamide from the
melt viscosity at the end point of the melt polymerization, it is
preferred to develop the estimating equation from the relative
viscosity and melt viscosity actually measured in several batches,
preferably in five batches or more. For example, the sampled
reaction solution is analyzed by a melt viscometer such as a melt
indexer and a flow tester to measure the melt viscosity and analyze
the relative viscosity. The following Equation C is formulated from
the results, by which the relative viscosity can be calculated from
the melt viscosity:
f.times.log(RV)=log(MV)+g/T+h (C)
[0036] wherein RV is relative viscosity, MV is melt viscosity
(Pa.s), T is temperature (.degree. C.), and f, g and h are
empirical constants.
[0037] The relative viscosity to be calculated from Equation C is a
common property for evaluating the polymerization degree of
polyamide, and corresponds to a relative viscosity calculated from
(dropping time of sample solution)/(dropping time of solvent),
where the solvent is sulfuric acid, fromic acid, etc. with a
specific purity (concentration), the sample solution is prepared by
dissolving polyamide into the solvent in a specific concentration,
and the dropping time is measured by a capillary viscometer.
[0038] The melt viscosity can be measured by analyzing a sampled
reaction solution by a melt viscometer such as a melt indexer and a
flow tester. However, a real time measurement of the melt viscosity
is more preferred. For the real time measurement, the batch
polymerization vessel is preferably equipped with a viscosity
analyzer such as a capillary viscometer. More easy and very
effective method for the real time measurement is to calculate the
melt viscosity from the stirring torque generated by the rotation
of stirring blade for stirring and mixing polyamide. This method
requires a torque meter for detecting the stirring torque which is
connected to the stirring blade. The stirring device usually
available is equipped with the torque meter. The relationship
between the stirring torque and the melt viscosity can be easily
expressed by an empirical or experimental equation. For example,
the melt viscosity can be calculated from the stirring torque and
the rotation number of the stirring blade using Equation D:
MV=i.times.ST/NR+j (D)
[0039] wherein MV is melt viscosity (Pa.s), ST is stirring torque
(N.m), NR is number of rotation (rpm), and i and j are empirical
constants.
[0040] The number of rotation of the stirring blade can be
corrected in Equation D and is not particularly limited, but the
number of rotation is preferably made constant to enhance the
accuracy of estimation with minimized error. The variation of the
number of rotation in the same batch and from batch to batch is
regulated preferably within .+-.5 rpm, more preferably within .+-.3
rpm.
[0041] The type of the stirring blade is not specifically limited
and various types of stirring blade such as anchor blade, ribbon
blade, double helical ribbon blade, grid blade, turbine blade,
paddle blade, propeller blade, disk blade, spectacle blade, and any
combination thereof may be used. In any event, it is preferred to
design the stirring blade so as to be sensitive to the difference
in the melt viscosity at the set point for calculating the mole
balance and at the end point for calculating the molecular weight
and relative viscosity. In addition, the stirring blade is required
to exhibit a sufficient stirring and mixing efficiency over the
viscosity range throughout the polymerization, for example, the
viscosity range of 0.01 to about 500 Pa.s.
[0042] In any of the methods for measuring the melt viscosity, the
detecting limit of the melt viscosity difference at the set point
during the melt polymerization is preferably 10 Pa.s or more, more
preferably 3 Pa.s or more, and still more preferably 1 Pa.s or
more.
[0043] In the present invention, the melt viscosity of polyamide is
measured at the set point during the melt polymerization and at the
end point of the melt polymerization. Since moisture has a
plasticizing effect on polyamide, the presence of moisture in a
large amount causes errors in the measurement of melt viscosity.
Therefore, the moisture content of polyamide around the set point
and the end point is preferably less than four times the saturated
moisture content, more preferably less than two times the saturated
moisture content. The pressure when measuring the melt viscosity,
particularly the pressure when measuring the stirring torque, which
significantly affects the moisture content, is preferably the same
as the pressure at the time when the above estimating equations are
formulated. The pressure variation from batch to batch is
preferably within .+-.10 kPa, more preferably within .+-.2 kPa.
[0044] To enhance the accuracy of the estimating equation for
calculating the melt viscosity of polyamide from the stirring
torque, the total amount of polyamide in the batch polymerization
vessel is preferably uniform from batch to batch. To ensure this,
the variation of total amount of the polyamide from the preceding
batch remaining in the batch polymerization vessel and the starting
material for polyamide newly charged into the batch polymerization
vessel is regulated preferably within .+-.{fraction (1/50)}, more
preferably within .+-.{fraction (1/100)}, and still more preferably
within .+-.{fraction (1/200)} of the average total amount between
batches which are conducted to develop the equation expressing the
relationship between the stirring torque and the melt
viscosity.
[0045] In the present invention, the point for measuring the
stirring torque during the melt polymerization may be any stage of
the melt polymerization as far as the pressure condition and the
total amount are uniform from batch to batch, as mentioned above.
However, to determine the subsequent polymerization conditions
(time, pressure, temperature) and the timing of discharge from the
melt viscosity, molecular weight and relative viscosity each being
calculated from the stirring torque, the stirring torque is
preferably measured at a middle or later stage of the
polymerization where the fixation of monomers is substantially
completed. As mentioned above, the pressure when measuring the
stirring torque should be uniform between batches. The number of
rotation of the stirring blade and the temperature at the measuring
point can be corrected, for example, in Equations A to C, and is
not needed to be uniform between batches. However, they are
preferably made uniform for ensuring the estimation with higher
accuracy. To attain estimation results with high accuracy, the
variation of the number of rotation at the measuring point is
regulated preferably within .+-.5 rpm, more preferably within .+-.3
rpm of the average number of rotation between batches which are
performed when the estimating equation is developed. The variation
of temperature is regulated preferably within .+-.5.degree. C.,
more preferably .+-.3.degree. C. of the average temperature between
batches which are performed when the estimating equation is
developed.
[0046] The pressure at the measuring point should be constant
within a batch as mentioned above, but the amidation history until
the measuring point is not needed to be the same. The number of
rotation and the temperature can be corrected, for example, in
Equations A to C, and are not needed to be constant within a batch.
However, they are preferably made constant for ensuring the
calculation with higher accuracy. To attain estimation results with
high accuracy, the variation of the number of rotation of stirring
blade is regulated preferably within .+-.5 rpm, more preferably
within .+-.3 rpm of the average number of rotation within a batch.
The variation of temperature is regulated preferably within
.+-.5.degree. C., more preferably .+-.3.degree. C. of the average
temperature within a batch.
[0047] The melt polymerization method of the present invention can
be practiced by a pressure method using a solution of nylon salt as
the raw material and a method where diamine is directly added to
molten dicarboxylic acid in the absence of solvent, with the later
method being preferred because the variation of reaction conditions
within a batch is small.
[0048] The method where diamine is directly added to molten
dicarboxylic acid in the absence of solvent is a melt
polymerization method effective for ensuring a batch-to-batch
uniformity in quality, because the addition amount of diamine in a
batch can be timely regulated based on the mole balance calculated
from the melt viscosity according the present invention.
[0049] Even if the viscosity properties (melt viscosity, molecular
weight, relative viscosity) of polyamide are made uniform from
batch to batch, the batch-to-batch uniformity of the mole balance
is still important, because the mole balance is a major factor to
change the viscosity properties during melt molding and melt
processing. The fixation of diamine is quite important for
controlling the mole balance. In the method where diamine is
directly added to molten dicarboxylic acid in the absence of
solvent, it is appear that a liquid diamine is more efficiently
fixed as compared with a gaseous diamine. Therefore, the use of a
diamine having a boiling point higher than the melting point of
polyamide being produce can avoid the use of high pressure for
fixing the diamine and enables the reaction at around atmospheric
pressure to reduce equipment costs. Thus, the boiling point of
diamine is preferably 5.degree. C. or more, more preferably
10.degree. C. or more higher than the melting point of polyamide.
The melting point of polyamide is the temperature of endothermic
peak attributable to the heat of crystal fusion observed in DSC
analysis. By heating the reaction system to temperatures higher
than the melting point, a uniform stirring and mixing can be
attained. In case of a hardly crystallizable or non-crystallizable
polyamide which shows no definite crystal fusion, the melting point
means a flow initiating temperature at which a uniform stirring and
mixing can be attained.
[0050] Examples of diamines suitably used as the diamine component
in the present invention include xylylene diamines such as m-, p-
and o-xylylene diamines and bis(aminomethyl)cyclohexanes such as
1,2-, 1,3- and 1,4-bis(aminomethyl)cyclohexanes. In view of
practical properties of resultant polyamide, if xylylene diamine is
used, the diamine component comprises preferably 50 mol % or more,
more preferably 70 mol % or more of m-xylylene diamine. If
bis(aminomethyl)cyclohexane is used, the diamine component
comprises preferably 50 mol % or more, more preferably 70 mol % or
more of 1,3-bis(aminomethyl)cyclohexane.
[0051] Examples of other diamines usable in the present invention
include tetramethylene diamine, pentamethylene diamine,
hexamethylene diamine, octamethylene diamine, nonamethylene
diamine, and p-phenylene diamine. A diamine having a boiling point
lower than melting point of polyamide +5.degree. C. may be used in
an amount of less than 30 mol % of the diamine component and in an
amount not making the fixation difficult.
[0052] Examples of dicarboxylic acids used as the dicarboxylic acid
component include adipic acid, succinic acid, sebacic acid,
dodecanedioic acid, isophthalic acid, terephthalic acid and
2,6-naphthalenedicarboxylic acid. These carboxylic acids may be
used alone or in combination of two or more. In view of practical
properties of resultant polyamide, the dicarboxylic acid component
preferably comprises adipic acid in an amount of 50 mol % or
more.
[0053] Examples of polyamide constituting components other than the
diamine and dicarboxylic acid include lactams such as caprolactam,
valerolactam, laurolactam and undecalactam, and aminocarboxylic
acids such as 11-aminoundecanoic acid and 12-aminododecanoic
acid.
[0054] In both the case of carrying out the present invention by
the pressure method using a solution of nylon salt as the raw
material and by the method where diamine is directly added to
molten dicarboxylic acid in the absence of solvent, the escape of
starting material, particularly, the escape of diamine component
out of the reaction system cannot be avoided. Therefore, the batch
polymerization vessel is required to have a partial condenser.
Water vapor and the diamine are separated in the partial condenser
and the diamine is returned to the polymerization vessel, thereby
effectively preventing the escape of diamine component. The
temperature of partial condenser is preferably 90 to 120.degree.
C., more preferably 95 to 115.degree. C., when the polymerization
is conducted under atmospheric pressure.
[0055] The solid phase polymerization of the present invention may
be carried out in any of batch manner, continuous manner and
semi-continuous manner. In the batch manner, the melt-polymerized
polyamide is solid phase-polymerized in an inert gas atmosphere or
under reduced pressure using a batch heating apparatus such as a
rotary drum. In the continuous manner, the melt-polymerized
polyamide is crystallized by heating under inert gas flow in a
grooved stirring-heating apparatus (pre-crystallization treatment),
and then solid phase-polymerized under inert gas flow in a hopper
heating apparatus. In the semi-continuous manner, the
melt-polymerized polyamide is crystallized in a grooved
stirring-heating apparatus, and then solid phase-polymerized in a
batch heating apparatus such as a rotary drum. As the batch heating
apparatus, a heating apparatus of rotary drum type called as tumble
dryer, conical dryer or rotary dryer, and a conical heating
apparatus having a rotary blade in its inside called as Nauta mixer
are preferably used, although not limited thereto.
[0056] The melt-polymerized polyamide and the solid
phase-polymerized polyamide produced in the present invention is
suitably used also as nano-composite materials and
oxygen-scavenging materials.
[0057] The present invention will be explained in more detail by
reference to the following examples which should not be construed
to limit the scope of the present invention. The measurements for
evaluations were carried out by the following methods.
[0058] (1) Stirring Torque
[0059] The stirring torque generated by the rotation of stirring
blade for stirring and mixing polyamide was read from a torque
meter connected to the stirring blade. Anchor blade was used as the
stirring blade and the measuring accuracy of stirring torque was
0.01 N.m.
[0060] (2) Melt Viscosity
[0061] After reading the stirring torque, molten polyamide was
discharged from the batch polymerization vessel, which was received
by a stainless receiver heated to the same temperature (about
260.degree. C.) as that of the reaction solution and then the melt
viscosity thereof was immediately measured by a flow tester
"CFT-500C" manufactured by Shimadzu Corporation under conditions of
981 kPa load, 1 mm.phi. die, 10 mm length, measuring temperature
which was the same as that of reaction solution when polyamide was
discharged, and one minute preheating time.
[0062] (3) Terminal Amino Concentration
[0063] After reading the stirring torque, molten polyamide was
discharged from the batch polymerization vessel, which was
solidified by cooling and dried. Into 30 cc of solvent of
phenol/ethanol=4/1 by volume, 0.3 to 0.5 g of accurately weighed
dried polyamide was dissolved under stirring at 20 to 30.degree. C.
The terminal amino concentration was measured by neutralization
titration of the resultant complete solution with a N/100
hydrochloric acid under stirring.
[0064] (4) Terminal Carboxyl Concentration
[0065] After reading the stirring torque, molten polyamide was
discharged from the batch polymerization vessel, which was
solidified by cooling and dried. Into 30 cc of benzyl alcohol, 0.3
to 0.5 g of accurately weighed dried polyamide was dissolved with
stirring at 160 to 180.degree. C. under nitrogen flow. After
cooling the resultant complete solution to 80.degree. C. under
nitrogen flow and adding 10 cc of methanol with stirring, the
terminal carboxyl concentration was measured by neutralization
titration with a N/100 aqueous solution of sodium hydroxide.
[0066] (5) Mole Balance
[0067] Determined by analysis based on second-order rate equation
of amidation using the measured terminal amino concentration and
terminal carboxyl concentration.
[0068] (6) Number Average Molecular Weight
[0069] Calculated from the following Equation E using the measured
terminal amino concentration and terminal carboxyl
concentration:
[0070] Number average molecular
weight=2.times.10.sup.6/([NH.sub.2]+[COOH]- ) (E) wherein
[NH.sub.2] is the terminal amino concentration (.mu.eq/g) and
[COOH] is the terminal carboxyl concentration (.mu.eq/g).
[0071] (7) Relative Viscosity
[0072] After reading the stirring torque, molten polyamide was
discharged from the batch polymerization vessel, which was
solidified by cooling and dried. Into 100 cc of a 96% sulfuric
acid, one gram of accurately weighed dried polyamide was dissolved
at 20 to 30.degree. C. with stirring. After competing the
dissolution, 5 cc of the resultant solution was placed in
Cannon-Fenske viscometer and allowed to stand for 10 min in a
thermostatic chamber of 25.+-.0.03.degree. C. Then, the dropping
time (t) was measured. The dropping time (t.sub.0) of the 96%
sulfuric acid itself was measured in the same manner. The relative
viscosity was calculated from the following Equation F using the
measured t and t.sub.0:
Relative viscosity=t/t.sub.0 (F).
EXAMPLES 1-4
[0073] (1) Development of Estimating Equation
[0074] After charging adipic acid, a stainless 50-L vessel equipped
with a stirrer, a torque meter, a partial condenser, a total
condenser, a nitrogen gas inlet and a dropping line was replaced
with nitrogen gas and then the temperature was raised to
190.degree. C. with stirring under a small amount of nitrogen flow
by heating with a heating medium. Then, m-xylylenediamine was
continuously added dropwise to molten adipic acid from the dropping
line under atmospheric pressure over two hours while stirring the
molten adipic acid at 40 rpm. The total amount of the charged
adipic acid and m-xylylenediamine was 25.00 kg. During the dropwise
addition, the inner temperature was continuously raised to
250.degree. C. Water being distilled with the dropwise addition of
m-xylylenediamine was removed from the reaction system through the
partial condenser and the total condenser each being kept at
100.degree. C. After completing the dropwise addition of
m-xylylenediamine, the pressure was held at atmospheric pressure
for 20 min with continuous stirring while raising the temperature
at a rate of 0.2.degree. C./min. Then, the pressure was decreased
to 80 kPa over 5 min and held there for 15 min. Thereafter, the
stirring torque at the set point was measured. Using the measured
stirring torque, the melt viscosity at the set point was calculated
from Equation D which was developed in advance by determining the
empirical constants from the measured values of stirring torque,
number of rotation and melt viscosity. Immediately after the
measurement of the stirring torque, polyamide was discharged and
solidified by water cooling, and the end group concentrations of
the solidified polyamide was analyzed.
[0075] The polymerization was repeated in the same manner as above
except for changing the mole balance of the resultant polyamide by
changing the charge mole balance variously while fixing the total
amount of adipic acid and m-xylylenediamine to 25.00 kg. From the
melt viscosity calculated from the measured stirring torque and the
mole balance calculated from the analyzed end group concentrations
of polyamide, the following estimating Equation G was obtained for
the mole balance range of 0.990 to 0.997. The number of samples was
6 and the correlation coefficient was 0.985.
Mole balance=0.0002689.times.melt viscosity (Pa.s)+0.9572 (G)
[0076] (2) Estimation of Mole Balance
[0077] Using the same polymerization apparatus and the same
polymerization conditions as used for developing the estimating
equation, polyamide was produced. The mole balance of the charged
adipic acid and m-xylylenediamine was adequately changed by using
an excess amount of adipic acid while taking the amount of monomer
to be escaped during the polymerization into consideration.
[0078] The melt viscosity calculated from the stirring torque
measured at the set point, the estimated mole balance calculated
from the estimating equation, and the measured mole balance
obtained from the end group concentrations of polyamide are shown
in Table 1. As seen from Table 1, the mole balance can be estimated
with an error within .+-.0.0003 of the measured values.
1 TABLE 1 Examples 1 2 3 4 Melt viscosity (Pa .multidot. s) 127.38
134.39 135.93 144.11 Estimated mole balance 0.9915 0.9933 0.9938
0.9960 Measured mole balance 0.9918 0.9930 0.9939 0.9960
EXAMPLES 5-8
[0079] (1) Development of Estimating Equation
[0080] Using 1,3-bis(aminomethyl)cyclohexane in place of
m-xylylenediamine, polyamide was produced in the same
polymerization apparatus as used in Example 1. After charging
adipic acid, the vessel was replaced with nitrogen gas and then the
temperature was raised to 180.degree. C. with stirring under a
small amount of nitrogen flow by heating with a heating medium.
Then, 1,3-bis(aminomethyl)cyclohexane was continuously added
dropwise to molten adipic acid from the dropping line under
atmospheric pressure over two hours while stirring the molten
adipic acid at 40 rpm. The total amount of the charged adipic acid
and 1,3-bis(aminomethyl)cyclohexane was 25.00 kg. During the
dropwise addition, the inner temperature was continuously raised to
245.degree. C. Water being distilled with the dropwise addition of
1,3-bis(aminomethyl)cyclohexane was removed from the reaction
system through the partial condenser and the total condenser each
being kept at 100.degree. C. After completing the dropwise addition
of 1,3-bis(aminomethyl)cyclohexane, the pressure was held at
atmospheric pressure for 20 min with continuous stirring while
raising the temperature at a rate of 0.3.degree. C./min. Then, the
pressure was decreased to 80 kPa over 5 min and held there for 15
min. Thereafter, the stirring torque was measured and polyamide was
discharged immediately thereafter. The melt viscosity at the set
point was calculated from Equation D which was developed in advance
by determining the empirical constants. Separately, the end group
concentrations of polyamide solidified by water cooling were
analyzed.
[0081] The polymerization was repeated in the same manner as above
except for changing the mole balance of the resultant polyamide by
changing the charge mole balance variously while fixing the total
amount of adipic acid and 1,3-bis(aminomethyl)cyclohexane to 25.00
kg. From the melt viscosity calculated from the measured stirring
torque and the mole balance calculated from the analyzed end group
concentrations of polyamide, the following estimating Equation H
was obtained for the mole balance range of 0.985 to 0.997. The
number of samples was 11 and the correlation coefficient was
0.939.
Mole balance=0.0001061.times.melt viscosity (Pa.s)+0.9741 (H)
[0082] (2) Estimation of Mole Balance
[0083] Using the same polymerization apparatus and the same
polymerization conditions as used for developing the estimating
equation, polyamide was produced. The mole balance of the charged
adipic acid and 1,3-bis(aminomethyl)cyclohexane was adequately
changed by using an excess amount of adipic acid while taking the
amount of monomer to be escaped during the polymerization into
consideration.
[0084] The melt viscosity calculated from the stirring torque
measured at the set point, the estimated mole balance calculated
from the estimating equation, and the measured mole balance
obtained from the end group concentrations of polyamide are shown
in Table 2. As seen from Table 2, the mole balance can be estimated
with an error within .+-.0.0004 of the measured values.
2 TABLE 2 Examples 5 6 7 8 Melt viscosity (Pa .multidot. s) 178.59
191.24 202.39 209.20 Estimated mole balance 0.9930 0.9944 0.9956
0.9963 Measured mole balance 0.9931 0.9946 0.9960 0.9962
COMPARATIVE EXAMPLE 1
[0085] The polymerization was conducted under the same conditions
and mole balance as in Example 7 while using
1,3-bis(aminomethyl)cyclohexane as the diamine. After reducing to
80 kPa, the pressure was held there for 5 min (10 min shorter than
in the case of Example 7). Thereafter, the melt viscosity was
calculated from the stirring torque and the mole balance was
calculated from Equation H. The calculated melt viscosity was 180.4
Pa.s. The estimated mole balance was 0.9935 and the measured mole
balance was 0.9957, indicating an error of 2/1000 or more of the
measured value.
COMPARATIVE EXAMPLE 2
[0086] The polymerization was conducted under the same conditions
and mole balance as in Example 5 except for changing the total
charged amount of adipic acid and 1,3-bis(aminomethyl)cyclohexane
to 25.80 kg. The melt viscosity calculated from the stirring torque
was 180.4 Pa.s. The estimated mole balance calculated from Equation
H was 0.9957, and the measured mole balance was 0.9930, indicating
an error of about {fraction (3/1000)} of the measure value.
[0087] As seen from Comparative Example 1, it is important for a
high estimating accuracy to make the polymerization history until
the set point for measuring the melt viscosity uniform from batch
to batch. Comparative Example 2 clearly shows that, for the
estimation of the mole balance from the melt viscosity calculated
from the stirring torque during the melt polymerization, it is
preferred to make the total amount of polyamide in the batch
polymerization vessel uniform from batch to batch, and shows that
the variation of the total amount is sure to cause estimating
errors.
EXAMPLES 9-13
[0088] (1) Development of Estimating Equation
[0089] After charging adipic acid, a stainless 50-L vessel equipped
with a stirrer, a torque meter, a partial condenser, a total
condenser, a nitrogen gas inlet and a dropping line was replaced
with nitrogen gas and then the temperature was raised to
190.degree. C. with stirring under a small amount of nitrogen flow
by heating with a heating medium. Then, m-xylylenediamine was
continuously added dropwise to molten adipic acid from the dropping
line under atmospheric pressure over two hours while stirring the
molten adipic acid at 40 rpm. The total amount of the charged
adipic acid and m-xylylenediamine was 25.00 kg. During the dropwise
addition, the inner temperature was continuously raised to
250.degree. C. Water being distilled with the dropwise addition of
m-xylylenediamine was removed from the reaction system through the
partial condenser and the total condenser each being kept at
100.degree. C. After completing the dropwise addition of
m-xylylenediamine, the pressure was held at atmospheric pressure
for 20 min with continuous stirring while raising the temperature
at a rate of 0.2.degree. C./min. Then, the pressure was decreased
to 80 kPa over 5 min and held there for a predetermined period of
time. After starting the holding at 80 kPa, the temperature of
heating medium was controlled so as to allow the temperature of
reaction solution (solution temperature) to reach 260.degree. C.
After holding at 80 kPa for a predetermined *period of time, the
solution temperature, the number of rotation and the stirring
torque were measured, and the polyamide was discharged immediately
thereafter to measure the melt viscosity, the end group
concentrations (number average molecular weight) and the relative
viscosity.
[0090] The same procedures were repeated while changing the charge
mole balance (m-xylylene diamine/adipic acid) within the range of
0.990 to 1.000 and changing the hold time at 80 kPa within the
range of 25 to 60 min, thereby determining the empirical constants
c to j of the estimating Equations B to D (number of
samples=15).
[0091] (2) Estimation of Melt Viscosity, Number Average Molecular
Weight and Relative Viscosity
[0092] Using the same polymerization apparatus as used for
developing the estimating equation, polyamide was produced under
the polymerization conditions shown in Table 3. The melt viscosity,
number average molecular weight and relative viscosity estimated
from the stirring torque, and the melt viscosity, number average
molecular weight and relative viscosity manually measured are shown
in Table 3.
3 TABLE 3 Examples 9 10 11 12 13 Hold time at 80 kPa (min) 60 40 25
25 40 Charge mole balance 0.991 0.995 0.997 1.000 0.993 Solution
temperature (.degree. C.) 259 258 257 257 258 Estimated values melt
viscosity (Pa .multidot. s) 216.2 222.5 222.8 228.6 218.3 number
average 16020 16770 16700 17470 16340 molecular weight relative
viscosity 2.09 2.14 2.13 2.18 2.11 Measured values melt viscosity
(Pa .multidot. s) 209.3 215.5 221.0 237.3 226.1 number average
15800 16400 16900 17500 16300 molecular weight relative viscosity
2.08 2.12 2.14 2.19 2.11
[0093] As seen from Table 3, the melt viscosity can be estimated
with an error within .+-.10 Pa.s of the measured value, the number
average molecular weight can be estimated with an error within
.+-.400 of the measured value, and the relative viscosity can be
estimated with an error within .+-.0.02 of the measured value. The
influence of factors such as the melt history in the polymerization
vessel and the mole balance on the estimated results was not found.
It can be also seen that the solution temperature can be corrected
in Equations B and C.
EXAMPLES 14-16
[0094] (1) Development of Estimating Equation
[0095] In this Example, the polymerization was conducted in the
same polymerization apparatus as used in Example 9 while using
1,3-bis(aminomethyl)cyclohexane in place of m-xylylenediamine.
After charging adipic acid, the vessel was replaced with nitrogen
gas and then the temperature was raised to 180.degree. C. with
stirring under a small amount of nitrogen flow by heating with a
heating medium. Then, 1,3-bis(aminomethyl)cyclohexane was
continuously added dropwise to molten adipic acid from the dropping
line under atmospheric pressure over two hours while stirring the
molten adipic acid at 40 rpm. The total amount of the charged
adipic acid and 1,3-bis(aminomethyl)cyclohexane was 25.00 kg.
During the dropwise addition, the inner temperature was
continuously raised to 245.degree. C. Water being distilled with
the dropwise addition of 1,3-bis(aminomethyl)cyclohexane was
removed from the reaction system through the partial condenser and
the total condenser each being kept at 100.degree. C. After
completing the dropwise addition of
1,3-bis(aminomethyl)cyclohexane, the pressure was held at
atmospheric pressure for 20 min with continuous stirring while
raising the temperature at a rate of 0.3.degree. C./min. Then, the
pressure was decreased to 80 kPa over 5 min and held there for a
predetermined period of time. After starting the holding at 80 kPa,
the temperature of heating medium was controlled so as to allow the
temperature of reaction solution (solution temperature) to reach
260.degree. C. After holding at 80 kPa for a predetermined period
of time, the solution temperature, the number of rotation and the
stirring torque were measured, and the polyamide was discharged
immediately thereafter to measure the melt viscosity, the end group
concentrations (number average molecular weight) and the relative
viscosity.
[0096] The same procedures were repeated while changing the charge
mole balance (1,3-bis(aminomethyl)cyclohexane/adipic acid) within
the range of 0.990 to 1.000 and changing the hold time at 80 kPa
within the range of 25 to 60 min, thereby determining the empirical
constants c to j of the estimating Equations B to D (number of
samples=15).
[0097] (2) Estimation of Melt Viscosity, Number Average Molecular
Weight and Relative Viscosity
[0098] Using the same polymerization apparatus as used for
developing the estimating equation, polyamide was produced under
the polymerization conditions shown in Table 4. The melt viscosity,
number average molecular weight and relative viscosity estimated
from the stirring torque, and the melt viscosity, number average
molecular weight and relative viscosity manually measured are shown
in Table 4.
COMPARATIVE EXAMPLE 3
[0099] The polymerization was conducted under the same conditions
as in Example 16 while using 1,3-bis(aminomethyl)cyclohexane as the
diamine. After completing the dropwise addition of
1,3-bis(aminomethyl)cyclohexane- , the pressure was held at
atmospheric pressure for 20 min with continuous stirring while
raising the temperature at a rate of 0.3.degree. C./min. The
pressure was further held at atmospheric pressure without
decreasing for additional 30 min. After the holding at atmospheric
pressure for 50 min, the solution temperature, the number of
rotation and the stirring torque were measured, and the polyamide
was discharged immediately thereafter to measure the melt
viscosity, the end group concentrations (number average molecular
weight) and the relative viscosity. The results are shown in Table
4.
COMPARATIVE EXAMPLE 4
[0100] The polymerization was conducted in the same manner as in
Example 16 except for changing the total charge amount of adipic
acid and 1,3-bis(aminomethyl)cyclohexane to 25.80 kg. The results
are shown in Table 4.
4 TABLE 4 Examples Comparative Examples 14 15 16 3 4 Hold time at
80 kPa (min) 60 40 25 atmospheric 25 pressure Charge mole balance
25 25 25 25 25.8 Solution temperature (.degree. C.) 261 258 256 256
256 Estimated values melt viscosity (Pa .multidot. s) 469.5 361.2
484.4 400.3 566.0 number average 16010 14610 15520 14770 16160
molecular weight relative viscosity 2.39 2.30 2.36 2.31 2.40
Measured values melt viscosity (Pa .multidot. s) 459.1 370.7 487.4
408.1 490.6 number average 16200 14800 15400 15600 15500 molecular
weight relative viscosity 2.41 2.31 2.35 2.35 2.35
[0101] As seen from Table 4, the melt viscosity can be estimated
with an error within .+-.10 Pa.s of the measured value, the number
average molecular weight can be estimated with an error within
.+-.200 of the measured value, and the relative viscosity can be
estimated with an error within .+-.0.02 of the measured value
(Examples 14-16). It can been seen that the melt viscosity, the
number average molecular weight and the relative viscosity can be
estimated from the stirring torque during the melt polymerization
even when the type of polyamide is changed.
[0102] On the other hand, as seen from Comparative Examples 3-4, it
is preferred for the estimation of the melt viscosity, molecular
weight and relative viscosity from the stirring torque to make the
pressure in the batch polymerization vessel uniform with the
pressure at the time when the estimating equation is determined,
because the pressure significantly affects the estimating accuracy
of the number average molecular weight and relative viscosity. In
addition, it can be seen that the total amount of polyamide in the
batch polymerization vessel is preferably uniform from batch to
batch, and the variation thereof is sure to cause estimating
errors.
EXAMPLE 17
[0103] Into molten adipic acid heated to 190.degree. C. in a
6-m.sup.3 stainless batch polymerization vessel equipped with a
stirrer, a torque meter, a partial condenser, a total condenser, a
nitrogen gas inlet and a dropping line, m-xylylenediamine was
continuously added dropwise from the dropping line under
atmospheric pressure over 140 min while stirring the molten adipic
acid at 40 rpm. The total charge amount of adipic acid and
m-xylylenediamine was 3500 kg. During the dropwise addition, the
inner temperature was continuously raised to 246.degree. C. Water
being distilled with the dropwise addition of m-xylylenediamine was
removed from the reaction system through the partial condenser and
the total condenser each being kept at 100.degree. C. After
completing the dropwise addition of m-xylylenediamine, the pressure
was held at atmospheric pressure for 20 min with continuous
stirring while raising the inner temperature to 250.degree. C.
Then, the pressure was decreased to 80 kPa over 5 min, held there
for 15 min, and then the inner temperature was raised to
256.degree. C. Immediately after reaching 256.degree. C., the
number of rotation of the stirring blade was changed to 20 rpm. The
point where the number of rotation reached 20 rpm was employed as
the set point, and the stirring torque there was measured. From the
result, the melt viscosity at the set point was calculated using
Equation D having its empirical constants determined in advance.
Thereafter, the melt polymerization was continued under the same
conditions while controlling the temperature of heating medium so
as to allow the inner temperature to reach 260.degree. C. After
holding for a predetermined period of time, the melt polymerization
was terminated and the stirring was stopped. The polyamide was
discharged from a die at a lower portion of the polymerization
vessel under a back pressure of nitrogen, and then solidified by
water cooling to obtain polyamide pellets. The point just before
the termination of the melt polymerization was employed as the end
point of the melt polymerization. Using Equation D, the melt
viscosity at the end point was calculated from the measured inner
temperature and stirring torque. The pellets of melt-polymerized
polyamide were analyzed for the mole balance, number average
molecular weight and relative viscosity.
[0104] The same procedures were repeated while changing the charge
mole balance (m-xylylene diamine/adipic acid) within the range of
0.990 to 1.000 and changing the hold time from the set point until
the end point within the range of 10 to 60 min, thereby determining
the empirical constants a to h of Equations A to C (number of
samples=10).
[0105] (2) Melt Polymerization
[0106] Melt polymerization was conducted in the same manner as in
the case of developing the estimating equations while changing the
charge mole balance (m-xylylene diamine/adipic acid) within the
range of 0.992 to 0.998 and changing the hold time from the set
point to the end point within the range of 10 to 40 min. The
melt-polymerized polyamides of 15 batches were estimated for the
mole balance, number average molecular weight and relative
viscosity from Equations A to C.
[0107] (3) Solid Phase Polymerization
[0108] Into a 13-m.sup.3 jacketed vacuum tumble dryer of batch
type, about 3000 kg pellets of the melt-polymerized polyamide from
each batch was charged. After replacing the dryer with nitrogen,
the temperature was started to be raised using a heating medium
under nitrogen atmosphere. The evacuation was started when the
inner temperature reached 120.degree. C. When the inner temperature
reached 140.degree. C. and thereafter, the evaluation of the number
average molecular weight of polyamide under solid phase
polymerization was started by successive calculation with one
minute update interval on the basis of second-order rate equation
of amidation while using estimated mole balance, estimated number
average molecular weight (taken as the number average molecular
weight at the initiation of solid phase polymerization),
temperature and pressure. The inner temperature was raised to
205.degree. C. When the calculated result of the number average
molecular weight of polyamide under solid phase polymerization
reached an aimed value, the pressure was returned to atmospheric
pressure by nitrogen and the cooling by heating medium was started.
When the inner temperature reached 60.degree. C., the pellets of
solid phase-polymerized polyamide were discharged to measure the
relative viscosity. The results of measurement of the relative
viscosity of the solid phase-polymerized polyamides of 15 batches
are shown in Table 5 and FIG. 2. The polyamide pellets could be
introduced into the vacuum tumble dryer immediately after melt
polymerization and the solid phase polymerization could be
initiated with little time lag, without needing time from the
completion of melt polymerization to the initiation of solid phase
polymerization.
COMPARATIVE EXAMPLE 5
[0109] (1) Melt Polymerization
[0110] Melt polymerization was conducted in the same manner as in
the case of developing the estimating equations of Example 17 while
changing the charge mole balance (m-xylylene diamine/adipic acid)
within the range of 0.992 to 0.998 and changing the hold time from
the set point to the end point within the range of 10 to 40 min.
The melt-polymerized polyamides of 15 batches were measured for the
mole balance, number average molecular weight and relative
viscosity by chemical analysis.
[0111] (2) Solid Phase Polymerization
[0112] The solid phase polymerization was conducted in the same
manner using the same apparatus as in Example 17. When the inner
temperature reached 140.degree. C. and thereafter, the evaluation
of the number average molecular weight of polyamide under solid
phase polymerization was started by successive calculation with one
minute update interval on the basis of second-order rate equation
of amidation while using measured mole balance, measured number
average molecular weight (taken as the number average molecular
weight at the initiation of solid phase polymerization),
temperature and pressure. The inner temperature was raised to
205.degree. C. When the calculated result of the number average
molecular weight of polyamide under solid phase polymerization
reached the value of Example 17, the pressure was returned to
atmospheric pressure by nitrogen and the cooling by heating medium
was started. When the inner temperature reached 60.degree. C., the
pellets of solid phase-polymerized polyamide were discharged to
measure the relative viscosity. The results of measurement of the
relative viscosity of the solid phase-polymerized polyamides of 15
batches are shown in Table 5 and FIG. 2. About six hours were taken
to chemically analyze the mole balance, number average molecular
weight and relative viscosity of the melt-polymerized polyamides,
and the solid phase polymerization could not be conducted until the
analysis of the melt-polymerized polyamide was completed.
5 TABLE 5 Comparative Example 17 Example 5 Number of samples
(number 15 15 of batches) Relative viscosity of solid
phase-polymerized polyamide average 2.61 2.61 maximum 2.65 2.66
minimum 2.59 2.53 standard deviation 0.02 0.04
[0113] As seen from Table 5, by estimating the properties of
melt-polymerized polyamide according to the method of the present
invention, the solid phase-polymerized polyamide having a relative
viscosity stable from batch to batch can be produced. It can be
found that the batch-to-batch stability is somewhat higher in the
present invention as compared with the method where the properties
are measured by chemical analysis. In addition, the solid phase
polymerization could be conducted in the present invention
immediately after the melt polymerization with no time lag, thereby
significantly enhancing the productivity.
[0114] The production method of polyamide of the present invention
has the following effects.
[0115] (1) The mole balance, molecular weight and relative
viscosity of polyamide under melt polymerization can be rapidly
estimated from the measured value of melt viscosity.
[0116] (2) Since the mole balance is easily obtained in real time,
the subsequent production conditions in a batch can be easily
controlled.
[0117] (3) Since the mole balance, molecular weight and relative
viscosity can be easily obtained in real time, the production
results of a batch can be rapidly reflected in the next and
subsequent batches.
[0118] (4) By estimating the melt viscosity from the stirring
torque, the mole balance, molecular weight and relative viscosity
can be easily estimated without needing expensive measuring
apparatus.
[0119] (5) Since the mole balance, molecular weight and relative
viscosity of melt-polymerized polyamide can be easily and rapidly
estimated, the conditions of solid phase polymerization can be
determined without delay.
[0120] (6) Since the mole balance, molecular weight and relative
viscosity can be easily and rapidly estimated, the conditions of
melt polymerization in the next and subsequent batches can be
easily controlled.
[0121] (7) By the estimation based on the stirring torque, the
properties of melt-polymerized polyamide (mole balance, molecular
weight, relative viscosity) can be easily estimated without needing
expensive measuring apparatus.
[0122] As describe above, the present invention provides a method
for easily determining and controlling the production conditions of
melt-polymerized polyamide and solid phase-polymerized polyamide,
and is of great industrial advantage.
* * * * *